It can lead to further things and it's very easy to hide
I had a half hour fling with an ex-gf in the first few years of marriage. 35 years later the wife had an internet fling with a guy, left and shacked up off and on for 4 years. When the flings excitement was gone I asked her if she finally considered her 4 year affair as making us 'even' for my half hour in bed with the ex? Her answer was 'nope'. infidelity hatred is definitely the longest lasting.
What’s the remedy then due, the “price”, to be back together? That’s the question.